The present invention relates to shafts having at least one functional body, manufactured separately from the shaft and then fastened on the shaft, such as assembled camshafts, which are mountable inside an internal combustion engine, as well as methods for producing such shafts and internal combustion engines equipped therewith.
Assembled camshafts, as well as methods for their production, in which separately produced cams are fixed on a shaft, are known, for example, from U.S. Pat. No. 6,286,196 (=DE 198 31 333), U.S. Pat. No. 6,804,884 (=DE 199 38 791) and US patent publication no. 2004/0134063 (=DE 101 01 539).
Assembled camshafts of this type provide an array of advantages in comparison to typical, forged camshafts. Thus, for example, cost reductions are achieved by producing the cams individually and then fastening the cams on the shaft, in particular because costly and complex forging tools and production processes are avoided, and because different materials, which are each optimal for the part in which they are used, may be used for the shafts and the cams. Further advantages, such as weight and cost reduction, also result if hollow shafts are used. Moreover, the principle of assembled camshafts allows significantly broader and more cost-effective flexibility in producing alterations, adaptations, and variants. In addition, the complex tempering of the entire shaft may be dispensed with.
The mounting of camshafts, whether with solid cams molded on in one piece, or separately formed cams assembled to a shaft, has been performed up to this point either via friction bearings or using split roller bearings, because closed, i.e., unitary bearings for use between two neighboring cams, could not be pushed axially over the cams because the cams have a larger diameter than the bearing journals. Therefore, it was not possible for the above-mentioned reasons to use camshafts as pre-assembled units and to exploit the mounting possibilities associated therewith, nor to fully exploit the advantages of roller bearings, such as lower power losses.
Additional types of assembled shafts for internal combustion engines to which the present invention also relates include, for example, balancer shafts and the like. The above-mentioned disadvantages also exist for such assembled shafts. Thus, up to this point, the bearings for such shafts in the corresponding housing sections of the internal combustion engine have been constructed as slide bearings or split roller bearings, at least to the extent that the bearings are envisioned for use between two balancing weights.